According to calculations by NASAs Jet Propulsion Laboratory (JPL), close approach data suggests the comet is most likely to make a close pass of 0.0007 AU (thats approximately 63,000 miles from the Martian surface). However, theres one huge caveat.

Due to uncertainties in the observations  the comet has only been observed for 74 days (so far), so its difficult for astronomers to forecast the comets precise location in 20 months time  comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles). But to the other extreme, its orbital pass could put Mars directly in its path. At time of Mars close approach (or impact), the comet will be barreling along at a breakneck speed of 35 miles per second

Since C/2013 A1 is a hyperbolic comet and moves in a retrograde orbit, its velocity with respect to the planet will be very high, approximately 56 km/s. With the current estimate of the absolute magnitude of the nucleus M2 = 10.3, which might indicate the diameter up to 50 km, the energy of impact might reach the equivalent of staggering 2×10¹º megatonnes! This kind of event can leave a crater 500 km across and 2 km deep. Such an event would overshadow even the famous bombardment of Jupiter by the disintegrated comet ShoemakerLevy 9 in July 1994, which by some estimates was originally 15 km in diameter.

All that is said above is based on the current measurements, and will of course be refined as more data comes in. In any case, even now we can say that the close approach will happen. The current orbit uncertainty allows for a collision scenario, but the possibility of this is small.

I don't know what kind of forming that would do to Mars, but it won't be terraforming!

Based on its magnitude I saw an size estimate of 50 km. If it is a sphere its volume would be 1.33*3.14*(25^3) or about 65,000 km^3. Assuming its mass is the same as water, we get 6.5*10^13 metric tons (I think). With little atmosphere to impede or ablate the comet, if it hits, it may be quite the show. I’ll leave it to someone else to do force and energy calculations.

I think we should be aiming water laden comets and asteroids at Mars to terraform it.

Specifically I think we should be trying to increase the mass of Mars so that it can better retain an atmosphere. It’ll need a bigger moon too, to help even out temperature fluctuations and add some internal heating from gravitational pull.

Some of the mirror and laser ideas that are being presented for asteroid deflection could probably work. We could send a swarm of mirrors out to deflect the astroid Apophis which could hit us in 2029 if we don’t. And then let these go on out to the asteroid belt and start deflecting asteroids towards mars.

It may very well be. Estimates of comet density average about .6g/cm^3 (of course the data is spotty). I selected the density of water as a standard because of its ease of use and the fact that it is a metric that most people understand. That said, the USDA standard for full fat ice cream is a minimum of 4.5 lbs/gallon. Conversion to the metric system gives a density of approximately 539 grams/liter or .539g/cm^3, slightly under the estimated average comet density. Recalculating the mass of the comet using the density of full fat ice cream, we arrive at 3.5*10^13 metric tons. If the collision takes place, it will still be a significant event.

"Specifically I think we should be trying to increase the mass of Mars so that it can better retain an atmosphere. Itll need a bigger moon too, to help even out temperature fluctuations and add some internal heating from gravitational pull."

It isn't necessary to make every world a duplicate of Earth. Variety is the spice, they say.

The good news is that you don't need to increase the mass of Mars. It's a nice thought, but who wants to wait around for that?

If you supplemented Mars' atmosphere up to about Earth pressure, it would take about a million years for it to leak away again. That's the good news.

The bad news is that the best gas to use for the purpose is carbon dioxide. So you still wouldn't be able to go shirtsleeve without a breathing supply and mask.

Planet Venus offers a plentiful supply of carbon dioxide, free for the taking, and most folks think that removing it would improve that planet too. Take all you want. If it leaks away, go back for more.

For me, it's not so important that humans be able to breathe the atmosphere of Mars without assistance; but I'd like to get it so that plants would feel at home there.

Imagine the size of trees grown in Martian soil and gravity!

And don't worry about a bigger Mars moon. We'll orbit it with a Rotavator. That should be exciting to watch!

47
posted on 02/26/2013 7:04:36 PM PST
by NicknamedBob
(If it was good enough for the Krell, then it's good enough for me!)

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